I tried gluing two bits of mdf together without screwing them, the glue expanded the mdf and they curved away from one another, I only noticed after the glue had set.
That explains it I suppose. I wonder has anyone tried a sandwich with Sorbothane in between the two wood panels? Sorbothane (Polyurethane) comes in different durometers (hardness or softness). It is very good at vibration reduction. I understand that to do this properly; it needs to be under some compressive force rather than just laying say a sheet inside by lining the panel interiors...
i am sure the trick is to have an elastic bond between the two sheets, when the bond (glue) gets hard then the two sheets acts like one single piece, which is something we do not want if we want inertness
but if we want to increase panel resonance frequency then a stiff glue is a good thing
i want the panels to sound like a quiet thud when hitting it and not anything like hitting an empty glass bottle
So maybe the secret then would be to use Sorbothane (or similar) under slight compression so it can effectively absorb vibrations between the two panels. This would take some experimenting to determine the right durometer and compressive force. Too much compression may possibly defeat the whole idea of a dampening medium; too little compression would maybe allow too much flex and not dampen very well...would be nice to have a scientific experiment to test all the possible configurations to arrive at the ideal "sandwich" construction...I certainly am not up to such a task, limited space and limited tools and machinery let alone lack of sophisticated test and measurement equipment that would be necessary to do a proper job here...
Hi,
There is no secret about CLD (constrained layer damping) this is an example ( not sorbothane used however but dedicated EAR product):
US5949033A - Constrained layer damped loudspeaker enclosure
- Google Patents
Earl Geddes explained here that there is a much easier way to achieve same goal (more or less) by the use of CLD approach to bracing ( not CLD to the enclosure walls but on bracing). More or less what Kef did to Ls50 enclosure or the way B&W tie the matrix skeleton parts together in the 800 series.
Make a search on this forum there was a patent about the cld bracing on the thread i'm thinking of ( it was in the last month iirc).
There is no secret about CLD (constrained layer damping) this is an example ( not sorbothane used however but dedicated EAR product):
US5949033A - Constrained layer damped loudspeaker enclosure
- Google Patents
Earl Geddes explained here that there is a much easier way to achieve same goal (more or less) by the use of CLD approach to bracing ( not CLD to the enclosure walls but on bracing). More or less what Kef did to Ls50 enclosure or the way B&W tie the matrix skeleton parts together in the 800 series.
Make a search on this forum there was a patent about the cld bracing on the thread i'm thinking of ( it was in the last month iirc).
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They do mention Sorbothane also but did not use it in this description or build. I guess I will attempt something along these lines for next major build; whenever that might be...
Ok so this may inspire you:
3-way active, time aligned, constrained layer construction
But i will insist on Earl Geddes advice: he knows what he is talking about as he used both way on Summa ( the enclosure started his life as a CLD he then switched to the CLD bracing method for ease of build if iirc). Will try to find the thread i talk about.
3-way active, time aligned, constrained layer construction
But i will insist on Earl Geddes advice: he knows what he is talking about as he used both way on Summa ( the enclosure started his life as a CLD he then switched to the CLD bracing method for ease of build if iirc). Will try to find the thread i talk about.
I can't find the thread but found the patent about bracing:
US7270215B2 - Loudspeaker enclosure with damping material laminated within internal shearing brace
- Google Patents
It gives the general idea. I'm surpised about dates as i think Earl Geddes did this prior to 2005 but i may be wrong.
US7270215B2 - Loudspeaker enclosure with damping material laminated within internal shearing brace
- Google Patents
It gives the general idea. I'm surpised about dates as i think Earl Geddes did this prior to 2005 but i may be wrong.
I don't know if this is the right material to use but this is what I've used rather than glue. Butyl Sealant Tape.
It's like silly putty but more sticky.
It's like silly putty but more sticky.
Material for Sound Proofing and Sound Dampening | Phelps Industrial Products
Found this article interesting in various product uses and descriptions.
Found this article interesting in various product uses and descriptions.
If you like the OB sound, go for it. If it was possible to replicate with a box, the speaker manufacturers would have done so.
I've built a Linkwitz Phoenix system and currently use ML Aeons hybrid electrostatic dipoles and have owned a pair of Quad ESL63s.
I wanted to sell the Aeons to raise some funds but I cannot live with any box speaker. I've tried Monitor Audio BX2, large bookshelf, Yamaha NSF51 floorstanders, and currently have some Q Acoustic 3050i medium floorstanders which are only used for home cinema audio, but the Aeons are the ones for music.
PHOENIX - Open Baffle Loudspeaker
If you have woodworking skills they are not difficult to build, though the crossover & equaliser is more involved.
I've built a Linkwitz Phoenix system and currently use ML Aeons hybrid electrostatic dipoles and have owned a pair of Quad ESL63s.
I wanted to sell the Aeons to raise some funds but I cannot live with any box speaker. I've tried Monitor Audio BX2, large bookshelf, Yamaha NSF51 floorstanders, and currently have some Q Acoustic 3050i medium floorstanders which are only used for home cinema audio, but the Aeons are the ones for music.
PHOENIX - Open Baffle Loudspeaker
If you have woodworking skills they are not difficult to build, though the crossover & equaliser is more involved.
it is almost hard to believe that cld bracings can be used instead of cld panels, either you must use many many bracings or a few but very large ones, unsupported areas of panels will still vibrate or ring?
If anyone's in Ohio... There's some new 1/2" felt panels.
1/2” Thick Felt Sound Board Colorbo Playground pad all purpose 48”x96” | eBay
I'd like to be able to get that much at that price!
1/2” Thick Felt Sound Board Colorbo Playground pad all purpose 48”x96” | eBay
I'd like to be able to get that much at that price!
Great link ... I can see somebody using that for room treatment. Combine some colors, overlay strips on a large sheet, lots of possibilities there.
Looking at that drawing in the link, what if one take a standard loudspeaker box and cut off about 2/3 cabinet from the back, would it become an open baffle speaker?
Another question, bit off topic, how to make a 3Ohm 2-way speaker box to a 4Ohm one? I haven't opened it yet.
Open baffle is a speaker without a back - i.e. open.
But the Phoenix uses electronics to smooth out the response, which will suffer when you have an open baffle. (the frontal sound travels round the side and cancels the rear sound so you need to use a mic to take measurements and determine the equalisation,unless you follow the dimensions and drivers on the Phoenix page.)
The good news is that the Linkwitz Riley transform crossovers /equalizers are available ready assembled from Ebay for £30 for a 3 way and about £20 for the 2way. It was really tedious building them on strip board 30years ago.
If your speaker is 3ohms impedance, which is unusual, just put a 1 ohm resistor in series if your amp is not happy driving them.
But the Phoenix uses electronics to smooth out the response, which will suffer when you have an open baffle. (the frontal sound travels round the side and cancels the rear sound so you need to use a mic to take measurements and determine the equalisation,unless you follow the dimensions and drivers on the Phoenix page.)
The good news is that the Linkwitz Riley transform crossovers /equalizers are available ready assembled from Ebay for £30 for a 3 way and about £20 for the 2way. It was really tedious building them on strip board 30years ago.
If your speaker is 3ohms impedance, which is unusual, just put a 1 ohm resistor in series if your amp is not happy driving them.
I thought the linkwitz transform where a circuit / compensation only for sealed cabinets to enhance the low frequency response?
Yes you are correct, I should have said Linkwitz Riley crossovers.
Active Filters
The transform works - I fitted two KEF B139 bass units into a sealed box (built in an old coffee table) and I have never heard such solid and powerful bass in any speaker since.
Active Filters
The transform works - I fitted two KEF B139 bass units into a sealed box (built in an old coffee table) and I have never heard such solid and powerful bass in any speaker since.